New research on drug usage in Japan has cast doubt on the idea that marijuana is an entry drug. The study found that people in Japan tend to start using cannabis after they have used alcohol or tobacco. They rarely use any other drugs.
Published this month in the journal Neuropsychopharmacology Reports, the research—which authors describe as “one of the largest and most significant studies on community-based cannabis users in Japan to date”—also found that nearly half of respondents who reported marijuana as their third drug “did not go on to use other substances afterward.”
The report, which is supported by both the Japanese Clinical Association of Cannabinoids and Ministry of Health, Labour and Welfare, concludes that “cannabis in Japan usually follows tobacco and alcohol, and seldom leads to further drug abuse.” The findings of this study challenge the hypothesis that the Japanese context is a gateway to drug use.
The research acknowledges that cannabis “is often labeled a ‘gateway drug,'” but it notes that “strong causal evidence for progression to other substances is limited.”
Its findings suggest that rather than cannabis use itself leading to other drug use, “shared vulnerabilities”—involving factors like age, educational background and socioeconomic status—”and strict drug policies may shape these patterns.”
A survey of 3,900 Japanese who used cannabis during their lives was carried out anonymously in January 2021. The respondents were asked about the use of other substances. The researchers then analysed the data in order to determine the likelihood of users using other substances after trying marijuana.
Authors wrote that the study’s results “do not imply a causal gateway of cannabis use, but rather highlight the need to take into account the larger life context of substance abuse.” The pattern of progression of substances is influenced by social factors such as the age group, socioeconomic status, and educational background.
The authors’ analysis of the results found that: “Odds of subsequent use of methamphetamine and illicit drugs following cannabis use are 1.25, 0.77 and 0.08 respectively. This suggests low probability of progression.”
While the results did show some correlations between lifetime marijuana consumption and use of some other drugs, such as methamphetamine, the 12-person team said that the findings failed to establish causality—the core claim of the gateway drug theory.
The report states that “Our survey showed that 10,4% of cannabis consumers reported having used methamphetamine in their lifetime, which is a much higher figure than the 0.5% estimated prevalence for methamphetamine usage among the Japanese general population.” This suggests cannabis users are more likely to be exposed to illegal drugs. However, this doesn’t prove causality.
Instead the study points to so-called “common liability theory,” under which “the observed order and relationship between substances result not from one drug directly leading to another, but from shared underlying factors—such as genetic, psychological, and social influences—that predispose individuals to multiple substance use.”
In Japan, the team says, “strict regulations on cannabis may lead to an environment where marijuana and other drugs are traded in the same illegal market. This increases the users’ exposure.” Thus, it may be the regulatory environment, rather than the pharmacological properties of cannabis itself, that creates a ‘gateway’ effect.”
A report from the University of California, Berkeley, found that “lifetime cannabis users” had a lower rate of using legal drugs such as prescription medications and benzodiazepines.
The authors did point out some limitations of the study. For example, the survey was self-selected and people were recruited who only reported lifetime cannabis usage rather than other drug use.
They wrote that future large-scale studies of the population would be crucial to overcome this limitation.
The new report concludes that “we have not observed patterns which support the hypothesis of gateway drugs.”
A study conducted in the United States last year concluded that, in spite of what the authors described as “substantial” increases in Schedule II stimulant consumption in the United States in recent times, the legalization and use of marijuana for adult purposes did not contribute to this increase. It was also shown that legalizing cannabis had a positive effect on stimulant consumption through the substitution process.
The authors of the study stated that the findings that marijuana prohibition was not linked with rising rates of stimulant use is contrary to their expectations when they began the project. They predicted that recreational cannabis legalization would increase stimulant usage but did not find any evidence of that.
Cannabis is sometimes referred to as a gateway drug, but a few studies have shown that it may act more like a replacement for other drugs among certain subgroups.
A survey released by the American Psychiatric Association (APA) and Morning Consult in 2023 found that Americans considered marijuana to be significantly less dangerous than cigarettes, alcohol and opioids—and they said cannabis is less addictive than each of those substances, as well as technology.
According to a Gallup study, Americans believe marijuana is less harmful that alcohol, cigarettes and tobacco products.
As for alcohol, a study published in November 2023 found that marijuana legalization may be linked to a “substitution effect,” with young adults in California “significantly” reducing their use of alcohol and cigarettes after the cannabis reform was enacted.
Recent research out of Canada also found a link between marijuana legalization and declines in beer sales, suggesting a substitution effect where consumers shift from one product to the other.
Other studies have linked cannabis legalization with reductions in the use of both prescription and nonprescription opioids. A report published last November, for example, linked legalizing medical marijuana with a “lower frequency” of nonprescribed pharmaceutical opioid use.
A 2023 federally funded study found that marijuana was significantly associated with reduced opioid cravings for people using them without a prescription, suggesting that expanding access to legal cannabis could provide more people with a safer substitute.
Separate research conducted in the same year showed that access to CBD-based products was associated with significant decreases in opioid prescriptions. The state level drops ranged from 6.6 to 8.1 percent.
Another linked medical marijuana use to lower pain levels and reduced dependence on opioids and other prescription medications, while yet another, published by the American Medical Association (AMA), found that chronic pain patients who received medical marijuana for longer than a month saw significant reductions in prescribed opioids.
AMA also released research showing that about one in three chronic pain patients report using cannabis as a treatment option, and most of that group has used cannabis as a substitute for other pain medications, including opioids.
State-level marijuana legalization is associated with major reductions in prescribing of the opioid codeine specifically, too, according to a study that leveraged data from the federal Drug Enforcement Administration (DEA).
A 2022 study similarly found that giving people legal access to medical cannabis can help patients reduce their use of opioid painkillers, or cease use altogether, without compromising quality of life.
There’s also no deficit of anecdotal reports, data-based studies and observational analyses that have signaled that some people use cannabis as an alternative to traditional pharmaceutical drugs like opioid-based painkillers and sleep medications.
Dominic Milton Trott provided the image.